1. Field of the Invention
The present invention relates to a waterproof joint for wireharness, and in particular to a waterproof joint for improving waterproofness at a wire connecting portion of wires of the wireharness.
2. Description of the Prior Art
Conventionally, various types waterproof structures for use in a wire connecting portion of wires of wireharness (herein after referred to as "joint section") have been proposed, since if water enters the joint section of the wireharness there may be caused many problems such as heating of resistors and ill-conduction because of generation of rust, or the like.
FIGS. 1 to 3 show one of such conventional waterproof structures for a joint section of a wireharness. In this waterproof structure, the joint section 150 in which a branch electrical wire 130 is connected to a main electrical wire 100 is embedded in a synthetic resin by injection molding so as to prevent water from entering therein.
Specifically, as shown in FIG. 1, in this joint section 150, an exposed conductor 140 of the wire 130 which is formed by partially stripping an insulating cover of the wire 130 is connected through a joint metal 200 to an exposed conductor 120 of the main wire 100 which is also formed by partially stripping an insulating cover 110 of the wire 100. The thus formed joint section 150 which is constituted from a connecting portion of the conductors and a part of the insulating cover of each of wires connected together is put into injection mold dies 300 and 300' as shown in FIG. 2. Thereafter, a synthetic resin that is softened by heat is poured into the dies 300 and 300', and then cooled and hardened, so that the joint section 150 is embedded in the synthetic resin 400 to form a waterproof joint as shown in FIG. 3.
FIGS. 4(a) and (b) show another conventional waterproof joint structure, in which a joint section of a wireharness is covered with a sealing member 500. In this waterproof structure, a joint section 150 of the main wire 100 and the branch wire 130 of the wireharness is formed in the same manner as the above prior art. Thus formed joint section 150 is covered with the sealing member 500 which includes an insulating sheet 510 and viscous and elastic waterproof compound 520 applied inside the insulating seat 510 in such a manner that the viscous and elastic waterproof compound 520 is placed on the inner side of the sealing member 500 when it is attached to the joint section 150.
FIG. 5 shows yet another conventional waterproof joint structure. Such type of waterproof joint structure is, for example, disclosed in Japanese Laid-open Patent Publication No. 52-17686 or Japanese Laid-open Utility Model Publication No. 62-123072. In this conventional waterproof joint, a joint section which has the same structure as those of the conventional joint sections as described above is covered with a thermal shrinkable tube 600. The thermally shrinkable tube 600 comprises an elastic thermal plastic adhesive 700 such as a heat fusion seal material or a butyl rubber applied on the inner side of the heat shrinkable tube 600. When the thermally shrinkable tube 600 is heated, the thermal plastic adhesive 700 is melted and then penetrates around the joint section 150 and into gaps or spaces between the wires 100 and 130 to achieve a seal of the joint section 150.
However, in the first conventional waterproof joint, although a sealing ability thereof is good, it requires to prepare molding equipment such as molding dies and an injection molding apparatus, thus leading to high costs in manufacturing the waterproof joints. Further, in this waterproof joint, it is necessary to prepare different type mold dies according to the types or sizes of wires to be connected, thus leading to troublesome parts control for the waterproof joints. Furthermore, there is another problem in that many branch wires can not be connected to the main wire due to space limitations in the dies. Moreover, in this waterproof joint, since it was required to put the joint section at the center of the dies in order to give a good sealability to the joint section, it was also necessary to accurately position the joint section with respect to the dies. This positioning operation is also troublesome.
Further, in the second conventional waterproof joint, it is necessary for the insulating sheet 510 to be massaged manually in order to fill the viscous waterproof compound 520 into spaces between the cables 100 130 when it is attached to the joint section 150. This means that productivity of the waterproof joint is not so good and that there is a possibility that some spaces or gaps would remain around the joint section, which deteriorates the sealability, so that quality stability may also be deteriorated.
Furthermore, in the third conventional waterproof joint employing the thermally shrinkable tube, there is a problem that if the number of wires to be connected is increased, the thermal plastic adhesive may not completely penetrate into spaces between the wires, thus resulting in unfavourable spaces therein. Further, according to this waterproof joint, since the thermally shrinkable tube is likely to be displaced with respect to the joint section 150 before heat is applied, there is a possibility that a part of the joint section 150 would be exposed from the tube. Furthermore, when the thermally shrinkable tube is attached to the joint section, the positioning of the tube with respect to the joint section is performed visually by an operator. Therefore, there is an unfavourable possibility that the joint section 150 would not be entirely covered by the thermally shrinkable tube, thus leaving a part of the joint section exposed or that uneven distribution of the thermal plastic adhesive would be caused in the tube, thus leasing to deterioration of the waterproofness of the waterproof joint.